全文获取类型
收费全文 | 44778篇 |
免费 | 3132篇 |
国内免费 | 40篇 |
专业分类
电工技术 | 313篇 |
综合类 | 27篇 |
化学工业 | 11122篇 |
金属工艺 | 755篇 |
机械仪表 | 965篇 |
建筑科学 | 1380篇 |
矿业工程 | 86篇 |
能源动力 | 882篇 |
轻工业 | 8403篇 |
水利工程 | 420篇 |
石油天然气 | 184篇 |
武器工业 | 5篇 |
无线电 | 1696篇 |
一般工业技术 | 7241篇 |
冶金工业 | 8576篇 |
原子能技术 | 157篇 |
自动化技术 | 5738篇 |
出版年
2024年 | 91篇 |
2023年 | 402篇 |
2022年 | 909篇 |
2021年 | 1760篇 |
2020年 | 1058篇 |
2019年 | 1163篇 |
2018年 | 1778篇 |
2017年 | 1759篇 |
2016年 | 1865篇 |
2015年 | 1462篇 |
2014年 | 1765篇 |
2013年 | 3411篇 |
2012年 | 2693篇 |
2011年 | 2657篇 |
2010年 | 2130篇 |
2009年 | 1956篇 |
2008年 | 1853篇 |
2007年 | 1734篇 |
2006年 | 1232篇 |
2005年 | 1012篇 |
2004年 | 921篇 |
2003年 | 819篇 |
2002年 | 793篇 |
2001年 | 560篇 |
2000年 | 490篇 |
1999年 | 570篇 |
1998年 | 2515篇 |
1997年 | 1744篇 |
1996年 | 1136篇 |
1995年 | 693篇 |
1994年 | 533篇 |
1993年 | 618篇 |
1992年 | 267篇 |
1991年 | 254篇 |
1990年 | 193篇 |
1989年 | 189篇 |
1988年 | 196篇 |
1987年 | 167篇 |
1986年 | 160篇 |
1985年 | 174篇 |
1984年 | 151篇 |
1983年 | 117篇 |
1982年 | 145篇 |
1981年 | 158篇 |
1980年 | 173篇 |
1979年 | 96篇 |
1978年 | 101篇 |
1977年 | 292篇 |
1976年 | 633篇 |
1973年 | 66篇 |
排序方式: 共有10000条查询结果,搜索用时 406 毫秒
81.
82.
Roberto C. Dante Pablo Martín-Ramos Pedro Chamorro-Posada Dario Rutto José Vázquez-Cabo Denisse G. Dante 《Fullerenes, Nanotubes and Carbon Nanostructures》2020,28(7):533-540
AbstractIn this work, a new g-C3N4-based Z-scheme with γ-Fe2O3 and β-Ag2Se both n-type semiconductors, and graphite to favor electron exchange is presented. The composite material was studied by XRD, FTIR, UV-Vis, TEM, XPS, TGA, DSC and TOF-SIMS, and the ability of this photocatalytic system to act as a photo-reductant was assessed using crystal violet (CV+) dye. Solar light driven photo-reduction of CV+ in the presence of tri-sodium citrate evidenced a synergistic enhancement of the activity of the composite toward reduction, with ~20 times higher conversion rates per unit of surface area than those of g-C3N4. Photo-oxidation experiments under Xe lamp irradiation in the presence of H2O2 also showed that the AgFeCN composite featured a higher activity (~8×) than g-C3N4. This Z-scheme may deserve further study as a photo-reductant to obtain hydrogen or hydrogenated compounds. Moreover, the use of CV+ may represent a facile procedure that can aid in the selection of new photocatalysts to be used in hydrogen production. 相似文献
83.
Juana Maria de Lourdes Medina-Contreras Patrick Mailloux-Salinas Juventino III Colado-Velazquez Norma Leticia Gomez Viquez Gómez-Viquez Rodrigo Velázquez-Espejel Ana del Carmen Susunaga-Notario David Julian Arias-Chávez Guadalupe Bravo 《Journal of the science of food and agriculture》2020,100(7):3212-3219
84.
Tsuchiya Letícia Diniz Braga Lucas Fiorini de Faria Oliveira Otávio de Bettio Raphael Winckler Greghi Juliana Galvani Freire André Pimenta 《Personal and Ubiquitous Computing》2021,25(2):281-295
Personal and Ubiquitous Computing - This article presents a study concerning the evaluation of a smart home control system for elderly people with a sample of 10 users in a city in the interior of... 相似文献
85.
86.
87.
88.
89.
Maria Grazia Basanisi Gianfranco La Bella Gaia Nobili Rosa Coppola Annita Maria Damato Maria Assunta Cafiero Giovanna La Salandra 《International Journal of Food Science & Technology》2020,55(3):1145-1150
The authenticity and traceability of meat products are issues of primary importance to ensure food safety. Unfortunately, food adulteration (e.g. the addition of inexpensive cuts to minced meat products) and mislabelling (e.g. the inclusion of meat from species other than those declared) happens frequently worldwide. The aim of this study was to apply a droplet digital PCR assay for the detection and quantification (copies μL−1) of the beef, pork, horse, sheep, chicken and turkey in meat products. The analysis conducted on commercial meat showed the presence of traces of DNA from other animal species than those declared. We show that the method is highly sensitive, specific and accurate (accuracy = 100%). This method could be adopted by competent food safety authorities to verify compliance with the labelling of meat products and to ensure quality and safety throughout the meat supply chain, from primary production to consumption. 相似文献
90.
Konstantin V. Dergilev Evgeny K. Shevchenko Zoya I. Tsokolaeva Irina B. Beloglazova Ekaterina S. Zubkova Maria A. Boldyreva Mikhail Yu. Menshikov Elizaveta I. Ratner Dmitry Penkov Yelena V. Parfyonova 《International journal of molecular sciences》2020,21(24)
Cell therapy of the post-infarcted myocardium is still far from clinical use. Poor survival of transplanted cells, insufficient regeneration, and replacement of the damaged tissue limit the potential of currently available cell-based techniques. In this study, we generated a multilayered construct from adipose-derived mesenchymal stromal cells (MSCs) modified to secrete stem cell factor, SCF. In a rat model of myocardium infarction, we show that transplantation of SCF producing cell sheet induced activation of the epicardium and promoted the accumulation of c-kit positive cells in ischemic muscle. Morphometry showed the reduction of infarct size (16%) and a left ventricle expansion index (0.12) in the treatment group compared to controls (24–28%; 0.17–0.32). The ratio of viable myocardium was more than 1.5-fold higher, reaching 49% compared to the control (28%) or unmodified cell sheet group (30%). Finally, by day 30 after myocardium infarction, SCF-producing cell sheet transplantation increased left ventricle ejection fraction from 37% in the control sham-operated group to 53%. Our results suggest that, combining the genetic modification of MSCs and their assembly into a multilayered construct, we can provide prolonged pleiotropic effects to the damaged heart, induce endogenous regenerative processes, and improve cardiac function. 相似文献